Axially prestressed coils out of a strip, in particular a steel strip, are used lately in place of bellows as longitudinally changeable protective sleeves for the protection of spindles, shafts and columns on machines. They have the advantage over bellows of having a substantially longer life and need less space. Because of their self-elasticity they extend by themselves, so that in general only an abutment is required and a fastening thereof to the machine parts which move relative to one another is not necessary.
A problem is the manufacture of such coils because the strip must be deformed permanently in a manner that the individual windings rest on one another with as little space as possible. If the play between the windings is too small, the windings jam in one another and the coil does not change as desired, which can also result in damage to the machine part which must be protected. When the play between the windings is too great, one obtains on the one hand undesired gaps, through which large chips can move, and on the other hand at the given winding number a large outside diameter of the coil, which is undesirable because of the limited space requirements. In relationship to the longitudinal axis of the axially resilient pretensioned spiral, which will be identified in short as a coil hereinafter, the individual windings have different sloped positions depending on the extension length. From this results an additional problem for the correct dimensioning of the winding spacing. Thus it is important to correctly coordinate the bending radius and the incline of the strip.
The basic purpose of the invention is to produce a machine, with which an exact coordination between the bending of the strip and its pitch is possible.
The inventive machine for the manufacture of a conical coil from a strip is characterized by a feed roller pair for feeding the strip by the use of an associated feed drive mechanism and the feed rollers can be moved against one another by a pressing device, a bending roller which is arranged in front of the feed roller pair, a bearing member for supporting the bending roller or the feed roller pair and which can be pivoted by means of a swivel drive mechanism about an axis extending perpendicularly to the plane of the strip which exits from the feed rollers and a shifting drive mechanism for shifting the bending roller or the feed rollers transversely to their axis and the feed drive mechanism, the swivel drive mechanism and the shifting drive mechanism being coupled with one another.
With the inventive machine it is possible to precisely coordinate the feed of the strip against the bending roller, the pivoting of the bending roller and its transverse shifting. The radius of curvature of the respective winding is determined by the degree of the relative transverse shifting between the bending roller and the feed rollers, while the pitch is defined by the swivelling position of the bending roller about the axis which extends at a right angle to the strip. If now these two adjusting movements are coordinated with one another and additionally with the feed of the strip, it is possible to manufacture a coil having a very certain pitch and an exactly defined increase of the radius of curvature of the windings. During the manufacture of a coil, first, a small radius of curvature is provided, which then increasingly becomes larger, since the windings are wound onto one another in a spiral-shaped manner. The length, which one wants to reach when the coil is completely relaxed, depends on the number of windings and the selected pitch. At the start and at the end it is possible to manufacture cylindrical windings, as this is needed as a rule in order to hold the coils well at their ends.
It is possible to make both the bending roller pivotal and movable parallel to its axis and to arrange the feed rollers stationarily, and also to support the bending roller nonmovably and instead arrange the feed rollers to be movable. Also the movability of both the feed rollers and also of the bending roller is conceivable. As a rule it will, however, be preferable to make only the bending roller pivotal and movable parallel to its axis, because this can be done easier structurally than the pivotal and movable arrangement of the feed rollers.
An important characteristic is the pressing device, which permits a clamping of the relatively thin and wide strip in such a manner that a deformation of the strip to form a coil is possible, without permitting the strip to shift between the feed rollers.
Differing from the embodiment illustrated in the drawings, coordination of the various adjusting movements can also be achieved by the drive mechanisms each having separate hydraulic or electric drive motors, which are coupled through a control device. The joining of the different adjusting movements thus does not need to be mechanical like in the illustrated exemplary embodiment, but can be achieved also with different conventional means familiar to the man skilled in the art.
The machine can also be equipped with a rotatably movable and longitudinally shiftable abutment for the forward moving coil end. The rotary movability of the abutment can be achieved both by the abutment being freely rotatably supported, for example on a ball bearing, and is carried along by the coil, and also by the abutment having an abutment drive mechanism associated therewith which drives the abutment synchronously with the rotation of the forward moving coil. Such an abutment prevents the windings from springing apart, which can be the case with pitches which are greater than the strip width.
According to a further development of the invention, a rotating support is provided, for example a roller pair or a pipe, on which rests the forward moving coil and this support has a drive mechanism associated therewith which drives the support synchronously with the rotation of the forward moving coil. Such a support is mainly of an advantage, when long coils are supposed to be manufactured.
In order to be able to influence the tapered position of the windings with respect to the axis of the coil according to a development of the invention, it is provided that the bending roller is positioned inclined relative to the bending edge which cooperates therewith and the angle of the sloped position can be preferably adjusted. As a result, a perfect function can be achieved during every extended condition of the coil, namely a jamming is avoided with the smallest possible play between the windings.